Exoskeletons are wearable mechanical devices that may possess a kinematic configuration similar to that of the human body and that may have the ability to follow the movements of the user's extremities. Powered exoskeletons may be designed to produce contact forces to assist the user in performing a motor task. In the past, a majority of the research on exoskeletons generally has focused on providing assistance to human limbs, where the assistance may potentially allow humans to carry loads with less effort (H. Kazerooni and R. Steger, “Berkeley lower extremity exoskeleton,” ASME J. Dyn. Syst., Meas., Control, vol. 128, pp. 14-25. 2006) and (L. M. Mooney, E. I. Rouse, and H. M. Herr, “Autonomous exoskeleton reduces metabolic cost of human walking during load carriage,” Journal of Neuroengineering and Rehabilitation, vol, 11, no. 80. 2014); walk faster (S. Lee and Y. Sankai, “Virtual impedance adjustment in unconstrained motion for an exoskeletal robot assisting the lower limb,” Advanced Robotics, vol. 19, no. 7, pp. 773-795, 2005) and (G. S. Sawicki and D. P. Ferris, “Mechanics and energetics of level walking with powered ankle exoskeletons,” J. Exp. Biol., vol. 211, no. Pt. 9, pp. 1402-1413, 2008) and provide torque assist to joints (J. E. Pratt, B. T. Krupp, C. J. Morse, and S. H. Collins, “The RoboKnee: An exoskeleton for enhancing strength and endurance during walking,” in Proc. IEEE Int. Conf. Robotics and Automation (ICRA), 2004, pp. 2430-2435) and (K. E. Gordon, C. R. Kinnaird, and D. P. Ferris, “Locomotor adaptation to a soleus emg-controlled antagonistic exoskeleton,” J. Neurophysiol., vol. 109, no. 7, pp. 1804-1814, 2013.).
Exoskeletons may be used to provide resistance to human motion. By providing resistance to human motion, the exoskeletons may be used for exercise and rehabilitation applications. Resistance training with upper body exoskeletons has been used in the past. (Z. Song and Z. Wang, “Study on resistance training for upper-limb rehabilitation using an exoskeleton device,” in Proc. IEEE Int'l Conf. Mechatronics and Automation, 2013, pp. 932-938); (Z. Song, S. Guo, M. Pang, S. Zhang, N. Xiao, B. Gao, and L. Shi, “Implementation of resistance training using an upper-limb exoskeleton rehabilitation device for elbow joint,” J. Med. Bio. Engg., vol. 34, no. 2, pp. 188-196, 2014) and (T.-M. Wu and D.-Z. Chen, “Biomechanical study of upper-limb exoskeleton for resistance training with three-dimensional motion analysis system,” J. Rehabil. Res. Dev., vol. 51, no. 1, pp. 111-126, 2014.). Upper body exoskeletons that may resist human motion with applications to tremor suppression have been used for rehabilitation (E. Rocon and J. L. Pons, Exoskeletons in Rehabilitation Robotics:Tremor Suppression. Springer Tracts in Advanced Robotics, 2011, pp. 67-98.). In 2013, NASA introduced the X1 exoskeleton ((2013) Nasa's x1 exoskeleton. http://www.nasa.gov/offices/oct/home/feature_exoskeleton.html). The X1 exoskeleton may be capable of providing both assistance and resistance to the joints in the leg. The X1 exoskeleton may be used as an exercise device that may improve the health of astronauts during their time in space, and may also be used for rehabilitation applications.
Even with previous efforts in exoskeleton design and implementation, there continues to be a need for a resistive exoskeleton control design framework that provides exoskeleton control parameters that achieve desired resistance. Therefore, it would be desirable to provide a system and method that overcome the above. The system and method would provide a resistive exoskeleton control design framework that provides exoskeleton control parameters that achieve desired resistance while ensuring that the resulting coupled system dynamics are both stable and passive.